Coal is a complex material that comprises both carbon-based chemical components and inorganic or mineral components that are herein collectively referred to as mineral components. The mineral components generally make up the ash content of the coal and play a significant role in determining the value of a particular coal. Generally, the higher the ash content of a coal, the lower is its value due to a correspondingly reduced energy content of the coal and the larger amount of waste that is produced during its use.
To separate such mineral components from coal, many procedures and processes are known in the art, including gravity separation, sedimentation and flotation. While coarse coal is readily separated from mineral impurities, fine coal (typically with a particle size of less than about 0.5 mm) is more difficult to separate and often lands up as “discard” coal in slurry dams from where it can either be re-worked, or dumped.
Mining and processing generally produce enormous quantities of coal fines that cannot be used in most normal coal applications such as energy generation as this coal is generally of low energy value due to the presence of large amounts of mineral components. Coal fines are also generally difficult to handle, process and transport.
Our earlier international patent application publication number WO 2012/025806 discloses that fine coal and other carbonaceous matter may conveniently be made available for use by agglomeration using microalgae biomass as binder for fine carbon particles.
Whilst it is expected that the present invention will predominantly be applied to coal fines per se, the expression coal fines should be interpreted broadly to embrace other carbonaceous fines such as may be experienced in the handling and processing of coke.